This invention relates generally to a coextruded film suitable for packaging, and more particularly to a hot blown film suitable for use in chub packaging and having improved tensile strength and seal strength properties.
Certain foods, and particularly meat products such as ground beef and other comminuted food substances, are commonly packaged in what are called chub packages. These packages are generally produced at central processing plants operated by supermarket chains or meat packing companies. These packages are generally produced using a vertical form fill seal (VFFS) process, in which a tube is formed from a flat sheet of roll stock film. The tube is formed vertically and longitudinally sealed with a vertical sealing bar. The bottom of the tube is then sealed with a clip applied to the bottom of the tube, the meat product such as ground beef is pumped into the open end of the tube, and the top is sealed with a clip to produce the final chub package. In appearance, these chubs resemble semi-rigid tubes with the tubular film forming a skin tight layer around the food product.
Package sizes may range from 1 to 20 pounds, depending on the intended mode of distribution. Pumping equipment typically used to stuff the food product into the tubular film can place great stress on the longitudinal seal of the tube. This longitudinal seal is usually a lap seal.
More recently, crust-frozen items have become more popular, and the hardening of the outer surface of the food product in the tubular casing during the freezing process can produce further stress on the longitudinal seal.
Successful films for use in such applications include the HS660 and HS 2000 films produced commercially by the Cryovac Division of W. R. Grace & Co. The films are composed of lay-flat tubular film. Prior to collapse, the HS660 film includes an inner layer of ethylene vinyl acetate copolymer (EVA) and an outer layer of polyethylene (PE). The two core layers comprise nylon, with an intermediate layer between each nylon layer and respective outer layer and inner layers comprising ionomer resins. In case of HS 2000, an ethylene vinyl alcohol copolymer replaces the nylon layer closest to the inside of the structure.
While such materials have been very useful in producing chub packaging, it is an object of the present invention to further improve the performance of chub packaging materials, especially under conditions wherein improved seal strength and lower transverse elongation are desirable.